Generac Power Systems 53187 - Manual (Page 92)

SECTION 3.3- COOLING
& VENTILATING AIR
I
Compensating for Restrictions
Air openings may be covered with louvers, ex­
panded metal or screening. These materials offer a
restriction to the flow or air. Such restrictions must be
compensated for by the installer.
To determine the actual air opening size required
when an air opening is covered by some material, the
material's "PERCENT OF FREE AIR INLET AREA“
must be known. This value can usually be obtained
from the manufacturer of the material. Some materials
may provide only a 60 percent free air inlet area. Even
the most efficient materials may offer only an 80-90
percent free air inlet area.
To calculate the actual air opening size required,
divide the unrestricted air opening size required by the
percent of free air inlet area of the material to be used.
PART 3- ENGINE
LUBRICATION & COOLING SYSTEM
EXAMPLE 1;
The recommended unrestricted air opening for
units with 15 inch stator Is 150 square inches. Air
openings are to be covered with a material having a 70
percent free air inlet area. Divide “150“ by “0.70" to
obtain “214.28 square inches“. In this case the actual
air opening size should be about 215 square inches.
EXAMPLE 2:
The recommended unrestricted air opening for
units with 10 inch stator is 300 square inches. Air
openings are to be covered by expanded metal having
an 80 percent free air inlet area. Divide *300 by 0.80’
to obtain “375 square inches“. The actual air opening
size should be about 375 square inches.
Figure 3. Typical Installation- Units with Suction Fan
PAGE 3.3-2